I have no actual knowledge that KM is multi-threaded. I don't think that it is. My KM 1.6.0 beta 2.4 runs well on my 4 core AMD cpu, but that is just because I have more RAM and my speed is three times that of my previous cpu.

No, it is not, and I don't say it by knowledge, it is just by observing the behavior. I may be wrong, then ;)

If you have an old PC and, therefore, it take "years" to open sites with heavy javascript load, you'll notice that the processor is using the % proportional to one of the cores. If you have 2 cores, you'll never see it passing much more (other system process involved) from 50%.

At least it is my case. I have a Hyper-Threading processor, then, so, 2 virtual cores, and is what happens.